This invention is an exceptionally flexible, ultrasoft vaso-occlusive or embolism forming device. It is made of a radiopaque material which may be a braid, coil, or chain which forms a long, thin threadlike device having little rigidity or column strength. The diameter of the device may be less than about 0.010 inches. The filamentary material making up the device used to form the coil, braid, or chain is typically of a diameter less than about 0.002 inches. The device is sufficiently flexible and small that it may be hydraulically delivered to a site within the vasculature of the human body using an injected drug or fluid flush through a catheter. In some configurations, the device may be delivered using pushers to mechanically deliver the device through the catheter lumen. Various mechanical connections may be used to sever the coil but a simple connection of a dissimilar metal to allow electrolytic separation upon application of a small voltage is desirable. The device assumes a random mass of threadlike material after being ejected from the catheter tip at the chosen vascular site. When the device is a coil, the coil may be a single or of multiple-helices. The device (whether coil or braid or chain) may be used alone or in conjunction with larger coils or braids to achieve a denser occlusion or with fibrous thrombotic attachments or as a substrate to localize the subsequent infusion of tissue adhesives, particulate embolization devices, or chemotherapeutic agents in abnormal blood vessels and tissues. The device may be used for the temporary occlusion of blood vessels during types of diminished blood flow testing. The invention also includes processes for introducing the devices into the human body.
Endovascular therapy has been used in treating a variety of different conditions, including control of internal bleeding, occlusion of blood supply to tumors, and relief of vessel wall pressure in the region of aneurysm. A variety of different embolic agents are known as arguably suitable for such therapy.
One known embolic agent includes injectable fluids or suspensions, such as microfibrillar collagen, various polymeric beads, and polyvinyl alcohol foam. The polymeric agents may be additionally crosslinked, sometimes in vivo, to extend the persistence of the agent at the desired vascular site. These agents are often introduced into the vasculature through a catheter. After such introduction, materials there form a solid space-filling mass. Although they provide good short-term vaso-occlusion, they are ultimately reabsorbed in the process of vessel recanalization.
Polymer resins, typically cyanoacrylates, are also employed as injectable vaso-occlusive materials. The resins are typically mixed with a radio-opaque contrast material or made radiopaque by the addition of tantalum powder. Their use is fraught with problems in that placement of the mixture is quite difficult. Inadvertent embolisms in normal vasculature (due to the inability of controlling the destination of the pre-gelled resins) is not altogether uncommon. The material is also difficult or impossible to retrieve once it has been placed in the vasculature. Such resins have not been FDA approved, and a waiver must be requested in each instance where the materials are applied during human operative procedures.
A number of mechanical vaso-occlusive devices are widely used. One such device is a balloon which may be carried to the vessel site at the end of the catheter and there inflated with a suitable fluid, typically a polymerizable resin, and released from the end of the catheter. The balloon device has the advantage that it effectively fills the cross-section of the occluded vessel. However, when using intravascular balloon embolization of intracranial berry aneurysms, inflation of a balloon into the aneurysm carries some risk of aneurysm rupture due to possible xe2x80x9coverfillingxe2x80x9d of portions of the sac and due to the traction produced when detaching the balloon from the end of the catheter. Moreover, a vascular balloon is difficult to retrieve after the resin within the balloon sets up, and the balloon cannot be easily visualized using radiographic techniques unless it is filled with contrast material. Balloons have also been known to rupture during filling, or release prematurely during filling, or leak monomeric resin into the vasculature during the period before the monomer sets up into polymeric form.
Another type of mechanical vaso-occlusive device is a wire coil or braid which can be introduced through a catheter in stretched linear form and assumes an irregular shape upon discharge of the device from the end of the catheter. A variety of vaso-occlusive coils and braids are known. For instance, U.S. Pat. No. 4,994,069, to Ritchart et al., shows a flexible, preferably coiled, wire for use in small vessel vaso-occlusion. Unlike vaso-occlusive coils previously, Ritchart et al. teaches a coil which is fairly soft and is delivered to the site using a pusher within a catheter lumen. The Ritchart et al. coils are typically pushed into the desired vascular site in a linear configuration. Upon discharge from the catheter, the coil may undertake any of a number of random or regular configurations designed to fill the site. The coils are used for small vessel sites, e.g., 0.5-6 mm in diameter. The coils themselves are said to be between 0.010 and 0.030 inches in diameter. The length of the coiled wire is typically 15-20 times the diameter of the vessel to be occluded. The wire used to make up the coils may be 0.002 to 0.006 inches in diameter. Tungsten, platinum, and gold threads or wires are said to be preferred. These coils have a variety of benefits, including the fact that they are relatively permanent, they can be easily imaged radiographically, they may be located at a well-defined vessel site, and they can be retrieved.
A variation of the mechanical endovascular coil is the electrolytically detached endovascular coil described in U.S. Pat. No. 5,122,132, to Guglielmi et al. Guglielmi""s coils are typically used in intracranial aneurysms because of their effectiveness in quickly forming controlled emboli. The disclosed coils are similar to those of Ritchart et al. in size and in composition. However, the method of introducing the coil to the vascular site is somewhat different. Rather than mechanically thrusting the coil into the chosen site, the coil is placed at the site and a small voltage is applied to the guidewire supporting the coil so that the coil is electrolytically detached from the distal tip of the guidewire. The step of electrolytically detaching the coil has the added benefit of forming a thrombus as the coil is detached. Again, as noted above, the Guglielmi coils may be stainless steel or platinum or the like, and are typically 0.010 to 0.020 inches in diameter and are made using wire having approximate diameters of 0.001 to 0.005 inches. The coils in this service are typically between 1 and 50 centimeters in length.
None of this background shows embolism-forming coils, braids, or chains having diameters less than about 0.010 inches in diameter, nor their placement by fluid delivery through a catheter.
This invention is an exceptionally flexible, ultrasoft vaso-occlusive or embolism device. It may be a braid, coil, or chain and is made of a radiopaque material forming a long, thin threadlike device having little rigidity or column strength. The diameter of the device may be less than about 0.010 inches, preferably less than about 0.0075 inches in diameter. The wire making up the device is typically of a diameter less than about 0.002 inches. The device is sufficiently flexible and small that it may be hydraulically delivered to a site within the vasculature of the human body using a catheter. The device may be mechanically delivered using a pusher wire. The devices may be severed from the pusher wire using a mechanical or electrolytic connection. Because of their flexibility and size, there is little opportunity for friction to develop with the catheter lumen.
These devices may be used with guide wirexe2x80x94directed catheters and with flow directed catheters, even those which are very flexible in their distal regions. This invention provides opportunities for placement of embolism-forming devices in vascular regions otherwise not routinely accessible due to their remote nature.
The device typically assumes a loose, random mass after being ejected from the catheter tip at the selected vascular site. When introduced into a high flow region, the mass quickly compacts into a significantly denser mass. The device, whether coil, braid, or chain, may be used in conjunction with larger coils, braids,or chains to achieve a denser occlusion or as a substrate to localize the subsequent infusion of tissue adhesives, particulate embolization devices, or chemotherapeutic agents in abnormal blood vessels and tissues, or for the temporary occlusion of blood vessels during types of diminished blood flow testing. The device may be coated with thrombotic or therapeutic materials or used in conjunction with fibrous embolic additions to the device. The invention also include processes for introducing the devices into the human body.
This invention is also a method for first introducing a larger vaso-occlusive device, such as a coil, to the vascular site desired by the attending physician, followed by the introduction of the inventive device so as to fill the interstices left by the larger coils and thereby form a denser occlusion. The devices may also be introduced by themselves, if so desired.